<b><i>CYP21A2</i></b> Gene Pathogenic Variants: A Multicenter Study on Genotype–Phenotype Correlation from a Portuguese Pediatric Cohort

Abstract

Background: Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21OHD) is an autosomal recessive disorder characterized by 3 overlapping phenotypes: salt-wasting (SW), simple virilizing (SV), and non-classic (NC). We aimed at conducting a nationwide genotype description of the CAH pediatric patients and to establish their genotype–phenotype correlation. Methods: CAH patients were recruited from Portuguese pediatric endocrinology centers and classified as SW, SV, or NC. Genetic analysis was performed by polymerase chain reaction (sequence specific primer, restriction fragment length polymorphism) or direct Sanger sequencing. Genotypes were categorized into 4 groups (0, A, B, and C), according to their predicted enzymatic activity. In each group, the expected phenotype was compared to the observed phenotype to assess the genotype–phenotype correlation. Results: Our cohort comprises 212 unrelated pediatric CAH patients (29% SW, 11% SV, 60% NC). The most common pathogenic variant was p.(Val282Leu; 41.3% of the 424 alleles analyzed). The p.(Val282Leu) variant, together with c.293-13A/C>G, p.(Ile173Asn), p.(Leu308Thr), p.(Gln319*), and large deletions/conversions were responsible for 86.4% of the mutated alleles. Patients’ stratification by disease subtype revealed that the most frequent pathogenic variants were c.293-13A/C>G in SW (31.1%), p.(Ile173Asn) in SV (46.9%), and p.(Val282Leu) in NC (69.5%). The most common genotype was homozygosity for p.(Val282Leu; 33.0%). Moreover, we found 2 novel variants: p.(Ile161Thr) and p.(Trp202Arg), in exons 4 and 5, respectively. The global genotype-phenotype correlation was 92.4%. Group B (associated with the SV form) showed the lowest genotype–phenotype correlation (80%). Conclusion: Our cohort has one of the largest NC CAH pediatric populations described. We emphasize the high frequency of the p.(Val282Leu) variant and the very high genotype–phenotype correlation observed.

Genetic characterization of a large cohort of Argentine 21‐hydroxylase Deficiency

“…The frequencies of c.293‐13A/C>G and DEL/LGC were also similar to those reported in Portugal 31 and in Argentine classical patients 17 . Our results may also support previous data reporting that DEL/LGC are less frequent in classical patients from our region 17,18 .…”

“…We confirmed an expected high frequency of the p.V282L variant because we included a ratio NC:C of almost 3:1 patients in our study. A recent study from Portugal in which 60% of the patients were NC reported similar results 31 . Within the NC group, the frequency of p.V282L was similar to the frequencies observed in other countries ranging from 45% to 69.5% 17,18,31‐36 …”

Characterization of Mutations Causing CYP21A2 Deficiency in Brazilian and Portuguese Populations

“…The p.W202R changed a heavy and hydrophobic residue to a hydrophilic and positively charged residue. This exchange at 202 abolished the enzyme activity (1.1% of WT), which is in agreement with the severe CAH (SW) form described for the patient [ 30 ]. In the other case, the leucine replacement by proline at position 199 broke the hydrogen bond with a residue on the same helix, destabilizing the conformation of helix F. Previous studies with helical substitution of leucine to proline at position 168 (helix E), 262 (helix H), and 322 (helix J) showed a break of the helix, as well, and association with the severe form of CAH [ 4 , 25 , 32 ].…”

Characterization of mutations causing steroid 21-hydroxylase deficiency in Brazilian and Portuguese populations

“…The p.W202R changed a heavy and hydrophobic residue to a hydrophilic and positively charged residue. This exchange at 202 abolished the enzyme activity, which is in agreement with the severe CAH (SW) form described for the patient [25]. In the other case, the leucine replacement by proline at position 199 broke the hydrogen bond with a residue on the same helix, destabilizing the conformation of helix F. Previous studies with helical substitution of leucine to proline at position 168 (helix E), 262 (helix H), and 322 (helix J) showed a break of the helix as well, and association with the severe form of CAH [4,19,27].…”